Twin‐screw extruders (TSE) are typically the equipment of choice in polymer blending and compounding operations due to the relatively high stresses and controllable residence times they impart on the melts. However, the mixing action is shear dominated and shear flows are energetically inefficient for dispersive mixing by comparison with extensional flows. We present a new extensional mixing element (EME), developed as a static dispersive mixing element for TSEs with dispersive mixing provided by extension‐dominated flow through stationary hyperbolically contracting channels. In Part 1 of the work, we present the design and show, experimentally and computationally, that the EME effectively imparts extension‐dominated flow through its channels. We also show that the flow is fully developed throughout most of the EME sections, with only small inlet transients being observed, and that it is possible to predict the real pressure drop in the system. Experimental validation of the EME for immiscible blends of varying viscosity ratios will be discussed in Part 2.
Conductometric titrations of the carboxylated CNCs with different charge density.From the conductometric titration plot, the difference between the points where the trend lines intersect is taken, representing the amount of 0.01 M NaOH used between these points. This value is
ABSTRACT:In Part 1 of this work, we presented a novel static extensional mixing element (EME) for twin-screw extrusion operations and validated the design in terms of the type of flow experienced by the melt upon dispersive mixing. In Part 2, we experimentally demonstrate the ability of the EME to yield improved dispersive mixing when compared with standard kneading-block-induced mixing for immiscible polypropylene/polystyrene blends of varying viscosity ratios between 0.3 and 10. The extensional flow characteristics of the EME improved the dispersion of polystyrene in the blends over all viscosity ratios, with improvements of 30% and above as measured by the cumulative area ratio measurements of polystyrene phases smaller than 1 μm 2 . The improvement in dispersive mixing seen from the EME for high viscosity ratio blends opens up applications in other areas, such as dispersion of nanoparticles or in reactive extrusion operations. C 2016 Wiley Periodicals, Inc. Adv Polym Technol 2016, 0, 21653; View this article online at wileyonlinelibrary.com.
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